1. Field of the Invention
The present invention relates to a water-repellent emulsion composition and a process for the production thereof. In particular, it relates to a water-repellent emulsion composition suitable as an aqueous-dispersion water repellent and a process for the production thereof.
2. Description of Prior Art
The deterioration of concrete structures has been one of the social issues of concern in recent years, and due to this, there have been developed a variety of water repellents to prevent the infiltration of external water, which is a main cause of the deterioration of concrete. These presently developed water repellents include solvent-base water repellents and aqueous-dispersion water repellents. The solvent-base water repellents involve problems in that they are liable to ignite and that they have high toxicity and really have a detrimental influence on a working environment and natural environment There is therefore an increasing demand for aqueous-dispersion water repellents having low flammability and low toxicity.
The aqueous-dispersion water repellent having the above advantages refers to a water-repellent emulsion prepared by dispersing a water-repellent substance in an aqueous dispersant For example there is known a water-repellent emulsion obtained by emulsifying alkylalkoxysilane as a water-repellent substance in water in the presence of a nonionic emulsifier as a dispersant (JP-A-62-197369).
Further, there are also disclosed an aqueous emulsion of an organic polysiloxane oil (U.S. Pat. No. 4,476,282) and a water-base dispersion of a silicon resin (U.S. Pat. No. 4,529,758).
Since, however, alkylalkoxysilane is highly hydrolyzable and requires a large amount of an emulsifier to be stable in water, there is a problem in that the water repellency decreases due to a large amount of the emulsifier which are incorporated to obtain an aqueous-dispersion water repellent having high dispersion stability.
Further, there is another problem in that the above aqueous emulsion of an organic polysiloxane oil and the above water-base dispersion of a silicon resin are still poor in water repellency and barrier properties against water absorption.
It is therefore an object of the present invention to provide an aqueous-dispersion water-repellent emulsion composition having high dispersion stability and having improved water repellency and improved barrier properties against water absorption, and a process for the production thereof.